Return string without trailing slash

I'd use a regular expression:

function someFunction(site)
{
// if site has an end slash (like: www.example.com/),
// then remove it and return the site without the end slash
return site.replace(/\/$/, '') // Match a forward slash / at the end of the string ($)
}

You'll want to make sure that the variable site is a string, though.

function stripTrailingSlash(str) {
    if(str.substr(-1) === '/') {
        return str.substr(0, str.length - 1);
    }
    return str;
}

Note: IE8 and older do not support negative substr offsets. Use str.length - 1 instead if you need to support those ancient browsers.

Try this:

function someFunction(site)     
{     
    return site.replace(/\/$/, "");
} 

ES6 / ES2015 provides an API for asking whether a string ends with something, which enables writing a cleaner and more readable function.

const stripTrailingSlash = (str) => {
    return str.endsWith('/') ?
        str.slice(0, -1) :
        str;
};